Printed Circuit Board And Method Of Manufacturing The Same

ABSTRACT

Disclosed are a printed circuit board and a method of manufacturing the printed circuit board. The printed circuit board includes an insulating layer, and a circuit pattern formed on the insulating layer, wherein the circuit pattern includes a first circuit pattern formed on the insulating layer and including a corner portion of an upper portion which has a predetermined curvature and a second circuit pattern formed on the first circuit pattern and configured to cover an upper surface of the first circuit pattern including the corner portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application claims priority under 35 U.S.C. §119 to KoreanPatent Application No. 10-2015-0116680, filed Aug. 19, 2015, which isherein incorporated by reference in its entirety.

BACKGROUND

The embodiment relates to a printed circuit board (PCB), and moreparticularly, a PCB including a first circuit pattern of which an upperportion has a curvature, a circuit pattern having a second circuitpattern formed on the first circuit pattern, and a top metal layerformed on the circuit pattern by electroplating and a method ofmanufacturing the same.

As the PCB is formed by printing a circuit line pattern on an electricalinsulating board with a conductive material such as copper, the PCB isreferred to as aboard just before electronic components are mountedthereon. That is, in order to mount various types of electroniccomponents on the planar surface, the PCB refers to a circuit boardhaving a planar surface on which a mounting position of each componentis fixed and a circuit pattern connecting the components is fixedlyprinted.

Generally, a surface processing method for a circuit pattern included inthe above-described PCB uses an organic solderability preservative (OSP)method, an electro nickel/gold method, an electro nickel/gold-cobaltalloy method, an electroless nickel/palladium/gold method, etc.

Here, the above-described surface processing methods is selected basedon the purpose of operation, for example, a use for soldering, a use forwire bonding, a use as connectors, etc.

FIG. 1 shows cross-sectional views of a process sequence for describinga method of manufacturing a PCB according to a conventional art, andFIG. 2 is a view illustrating an upper surface of the PCB according tothe conventional art.

Referring to FIG. 1A, first, an insulating layer 10 is provided, and aseed layer 20 is formed on the provided insulating layer 10.

Further, a mask 30 including an opening (not shown) which exposes atleast a part of an upper surface of the seed layer 20 is formed on theformed seed layer 20.

Then, electroplating is performed based on the seed layer 20, and acircuit pattern 40 under which the opening of the mask 30 is buried isformed on the seed layer 20.

Then, referring to FIG. 1B, when the circuit pattern 40 is formed, agrinding process for planarization of an upper surface of the formedcircuit pattern 40 is performed.

While performing the grinding process, at least a part of the upperportion of the circuit pattern 40 spreads inside of the mask 30, andthus, an upper end portion of the circuit pattern 40 includes aprotrusion (not shown) protruding in a direction of the mask 30.

Then, referring to FIG. 1C, a preprocessing process for performing asurface processing process is performed.

Here, the preprocessing process is performed using an acid-basedchemical for etching a surface of the circuit pattern 40. At this point,when the preprocessing process is performed, the etching is performednot only on the upper surface of the circuit pattern 40 but also onboundary surfaces of upper and side surfaces of the circuit pattern 40.

Thus, when the preprocessing process is performed, each corner portion50 of the circuit pattern 40 has a predetermined curvature in a convexshape.

In other words, when the preprocessing process is performed, gaps aregenerated between the mask 30 and the circuit pattern 40.

Further, in the conventional art, with the gaps generated as shown inFIG. 2, a surface processing process is performed on the circuit pattern40 to form a top metal layer 60.

However, when the top metal layer 60 is formed with the gaps generated,the top metal layer 60 is also formed on the corner portions 50 of thecircuit pattern 40.

Accordingly, as shown in FIG. 2, the top metal layer 60 according to theconventional art may include a protrusion 70 protruding in a directionof a side surface of the circuit pattern 40, and this makes a big impacton the reliability of the PCB.

BRIEF SUMMARY

The embodiment provides a printed circuit board (PCB) having a newstructure and a method of manufacturing the same.

In addition, the embodiment provides a PCB formed by electroplating atop metal layer of a circuit pattern using a plating seed layer used inthe formation of the circuit pattern and a method of manufacturing thesame.

Further, the embodiment provides a PCB including a first circuit patternof which at least a part of a corner portion has a curved surface and acircuit pattern including a second circuit pattern which is formed onthe first circuit pattern and covers a corner portion of the curvedsurface, and a method of manufacturing the same.

Furthermore, the embodiment provides a PCB including a top metal layerformed on the second circuit pattern, having a width greater than awidth of the second circuit pattern, and configured to protrude from aside surface of the second circuit pattern to the outside, and a methodof manufacturing the same.

The objectives of the present invention are not limited to the above,and other objectives will be clearly understood to those skilled in theart from the following descriptions.

According to the embodiment, there is provided a PCB including aninsulating layer; a plating seed layer disposed on the insulating layer;a circuit pattern disposed on the plating seed layer; and a top metallayer disposed on the circuit pattern, wherein the circuit patterncomprises: a first circuit pattern disposed on the plating seed layer,and a second circuit pattern disposed on the first circuit pattern andincluding a same metallic material as the first circuit pattern.

According to the embodiment, there is provided a PCB including aninsulating layer; a plating seed layer disposed on the insulating layer;a first circuit pattern disposed on the plating seed layer and directlycontacted with the plating seed layer; a second circuit pattern directlycontacted with the first circuit pattern and formed of copper; and a topmetal layer directly contacted with the second circuit pattern andformed of gold (Au), wherein the top metal layer has a wider width thana width of the second circuit pattern.

According to the embodiment of the present invention, a flash platingprocess is performed to fill corner portions of a circuit pattern etchedduring a preprocessing process, then a surface processing process isperformed with the corner portions filled, and thus a failure of the topmetal layer due to overspreading can be removed, thereby the reliabilityof a PCB can be improved.

In addition, according to the embodiment of the present invention, sincea top metal layer is formed by utilizing a plating seed layer used inthe formation of a circuit pattern, one of electrolytic surfaceprocessing and electroless surface processing methods is selectablewithout a design restriction.

Further, according to the embodiment of the present invention, since atop metal layer including gold (Au) is formed using the plating seedlayer used in the formation of the circuit pattern, a nickel (Ni) topmetal layer serving as a seed layer function of a conventional gold (Au)top metal layer can be removed, and thus a thickness of a product can belowered, and product cost can also be lowered due to the removal of thenickel top metal layer.

Furthermore, according to the embodiment of the present invention, sincea portion, protruding from a side surface of the circuit pattern to theoutside, of the top metal layer is minimized by performing the flashplating process, the structural stability of the top metal layer can besecured.

Further, according to the embodiment of the present invention, a problemof cracks occurring between a Cu layer which forms a circuit pattern andan Au layer which is a surface processing layer of the circuit patterncan be solved, delamination of each layer and occurrence of voids causedby the cracks can then be suppressed, and reliability of a printedcircuit board can thus be improved.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C show cross-sectional views of a process sequencefor describing a method of manufacturing a printed circuit board (PCB)according to a conventional art.

FIG. 2 is a view illustrating an upper surface of the PCB according tothe conventional art.

FIG. 3 is a cross-sectional view illustrating a structure of a PCBaccording to an embodiment of the present invention;

FIG. 4 is an enlarged view of a portion A shown in FIG. 3.

FIG. 5 is a flowchart of a process sequence for describing a method ofmanufacturing the PCB according to the embodiment of the presentinvention.

FIGS. 6 to 15 are cross-sectional views of the process sequence fordescribing the method of manufacturing the PCB shown in FIG. 3.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present invention that areeasily performed by those skilled in the art will be described in detailwith reference to the accompanying drawings. However, the presentinvention may be implemented in various different forms and is notlimited to the embodiments described herein.

In the following description, when there is an expression that someportion “includes” some structural elements, this means that someportion does not exclude another structural element, but may furtherinclude another structural element unless stated to the contrary.

Further, structures and elements which do not relate to the detaildescription are not shown in the drawings to clearly describe thepresent invention, thicknesses may be exaggerated to clearly explainvarious layers and regions, and similar elements in the followingdescription are designated by similar reference numerals.

It will be understood that when a portion of a layer, a film, a region,a plate or the like is referred to as being “on” another portion, it canbe “directly formed on” another portion, or a third portion can beinterposed between the portions. Otherwise, when a portion is “directlyformed on” another portion, it means that there is no third portionbetween the portions.

The embodiment of the present invention provides a new printed circuitboard (PCB) on which a surface processing process may be performed afterfilling corner portions, etched by a preprocessing process, of a circuitpattern based on a flash process and a method of manufacturing the same.

FIG. 3 is a cross-sectional view illustrating a structure of a PCBaccording to an embodiment of the present invention, and FIG. 4 is anenlarged view of a portion A shown in FIG. 3.

Referring to FIGS. 3 and 4, a PCB 100 includes an insulating layer 110,a plating seed layer 120, a circuit pattern 150, and a top metal layer160.

The insulating layer 110 may be a support board of a PCB on which asingle circuit pattern is formed or may be an insulating layer region,in which the circuit pattern 150 is formed, of a PCB having a stackedmultilayer structure.

When the insulating layer 110 refers to an insulating layer included inthe stacked multilayer structure, a plurality of circuit patterns may beconsecutively formed on an upper surface or lower surface of theinsulating layer 110.

The insulating layer 110 may form an insulating plate, may be athermosetting or thermoplastic polymer board, a ceramic board, anorganic-inorganic composition material board, or a fiberglass immersionboard, and when a polymer resin is included, an epoxy-based insulatingresin may be included, otherwise, a polyimide-based resin may also beincluded.

The circuit pattern 150 is formed on the insulating layer 110.

Preferably, the plating seed layer 120 used in the formation of thecircuit pattern 150 is formed between the insulating layer 110 and thecircuit pattern 150.

Widths of upper and lower surfaces of the plating seed layer 120 may bethe same. Here, the width may refer to an actual length.

In other words, a width of the upper surface of the plating seed layer120 refers to an actual length from one end of the upper surface of theplating seed layer 120 to the other end, and a width of the lowersurface of the plating seed layer 120 refers to an actual length fromone end of the lower surface of the plating seed layer 120 to the otherend. Accordingly, a width described below may be defined as an actuallength from one end to the other end as in the above.

Further, the circuit pattern 150 is formed on the plating seed layer120.

The circuit pattern 150 may also have a shape in which widths of upperand lower surfaces thereof are the same similarly to those of theplating seed layer 120.

The plating seed layer 120 and the circuit pattern 150 are formed ofpure copper or a conductive metal material having copper (Cu).

The circuit pattern 150 may be formed by a general process ofmanufacturing a PCB, such as an additive process, a subtractive process,a modified semi additive process (MSAP), a semi additive process (SAP),etc., and detailed descriptions thereof will be omitted herein.

At this point, the circuit pattern 150 includes a first circuit pattern130 of which corner portions of an upper portion have a predeterminedcurvature and a second circuit pattern 140 which is formed on the firstcircuit pattern 130 and covers the corner portions of the first circuitpattern 130.

That is, the circuit pattern 150 includes the first circuit pattern 130in which boundary portions of upper and side surfaces thereof haveconvexly curved surfaces by having the corner portions removed during apreprocessing process.

Further, the second circuit pattern 140 is disposed on the first circuitpattern 130.

The second circuit pattern 140 is formed to cover the convexly curvedsurfaces of the first circuit pattern 130. In other words, the secondcircuit pattern 140 fills the corner portions of the first circuitpattern 130 removed during the preprocessing process.

An upper surface of the second circuit pattern 140 may be planar, and alower surface thereof may have a curvature corresponding to a curvatureof the corner portion of the first circuit pattern 130.

At least a part of a lower end of the second circuit pattern 140 ispositioned at a lower level than an upper end of the first circuitpattern 130.

That is, the second circuit pattern 140 is formed to cover the cornerportions of the first circuit pattern 130, and the corner portions areboundary surfaces of the upper and side surfaces of the first circuitpattern 130. In other words, the corner portions of the first circuitpattern 130 include a part of the upper surface and a part of the sidesurface of the first circuit pattern 130.

Accordingly, the second circuit pattern 140 is formed to substantiallycover a part of the upper and side surfaces of the first circuit pattern130.

Thus, a part of the lower end of the second circuit pattern 140 extendsup to a side surface portion of the first circuit pattern 130 and isthus positioned at a lower level than the upper end of the first circuitpattern 130.

The top metal layer 160 is formed on the circuit pattern 150.

The top metal layer 160 may be formed of a metal including only gold(Au) or may be formed of an alloy including gold (Au).

When the top metal layer 160 is formed of the alloy including gold (Au),the top metal layer 160 may be formed of a gold alloy including cobalt.At this point, the top metal layer 160 is formed by electroplating.

Preferably, the top metal layer 160 is formed by electroplating on theplating seed layer 120 which is the same layer as the plating seed layerused in the formation of the circuit pattern 150.

The top metal layer 160 is formed on the circuit pattern 150, and thus alower surface of the top metal layer 160 is in direct contact with anupper surface of the circuit pattern 150. More specifically, the lowersurface of the top metal layer 160 is in direct contact with an uppersurface of the second circuit pattern 140 of the circuit pattern 150.

At this point, the top metal layer 160 includes a lower surface having awidth greater than a width of the upper surface of the circuit pattern150.

Accordingly, the lower surface of the top metal layer 160 includes afirst lower surface in direct contact with the upper surface of thecircuit pattern 150 and a second lower surface not in contact with theupper surface of the circuit pattern 150.

Here, the first lower surface of the top metal layer 160 may be acentral region of the lower surface of the top metal layer 160, and thesecond lower surface of the top metal layer 160 may be left and rightregions of the top metal layer 160.

Further, the top metal layer 160 may have a shape in which widths ofupper and lower surfaces thereof are the same.

Meanwhile, the upper and lower surfaces of the top metal layer 160 mayhave widths greater than the width of the lower surface of the circuitpattern 150.

Accordingly, as shown in FIGS. 3 and 4, the top metal layer 160 includesa protrusion protruding from the upper portion of the circuit pattern150 to the outside of the side surface of the circuit pattern 150. Theprotrusion is a portion corresponding to the second lower surface of thetop metal layer 160.

As described above, since the top metal layer 160 including gold (Au) isformed using the plating seed layer 120 used in the formation of thecircuit pattern 150 according to the embodiment of the presentinvention, a nickel (Ni) top metal layer serving as a seed layerfunction of a conventional gold (Au) top metal layer may be removed.

Although the drawings illustrate that one circuit pattern 150 is formedon the insulating layer 110, the circuit pattern 150 may be formed on atleast any one surface of upper and lower surfaces of the insulatinglayer 110 as multiple patterns having a regular gap.

When the circuit pattern 150 is described in more detail with referenceto FIG. 4, the circuit pattern 150 includes the first circuit pattern130 formed on the plating seed layer 120 having a lower surface incontact with an upper surface of the plating seed layer 120 and thesecond circuit pattern 140 formed on the first circuit pattern 130 andhaving at least a part of an upper surface in contact with the lowersurface of the top metal layer 160.

Here, although it has been described that the circuit pattern 150 isprovided with the first circuit pattern 130 and the second circuitpattern 140 as a plurality of layers, since the first circuit pattern130 and the second circuit pattern 140 are formed of the same material,the first circuit pattern 130 and the second circuit pattern 140 aresubstantially formed as a single layer.

A lower surface of the first circuit pattern 130 of the circuit pattern150 is formed being in direct contact with the upper surface of theplating seed layer 120.

At this point, corner portions of an upper portion of the first circuitpattern 130 of the circuit pattern 150 are formed to have apredetermined curvature in a lengthwise direction. Preferably, thecorner portions of the first circuit pattern 130 are formed to have aconvex curvature in the lengthwise direction.

The corner portions are boundary portions of upper and side surfaces ofthe first circuit pattern 130 and thus include a part of the uppersurface and a part of the side surface.

Further, the second circuit pattern 140 of the circuit pattern 150 isformed on the first circuit pattern 130 and covers the corner portionsof the first circuit pattern 130.

That is, the lower surface of the second circuit pattern 140 of thecircuit pattern 150 is formed to have a predetermined curvaturecorresponding to the curvature of the corner portion of the firstcircuit pattern 130.

Meanwhile, the circuit pattern 150 includes the first circuit pattern130 and the second circuit pattern 140, wherein the second circuitpattern 140 is formed on the upper surface of the first circuit pattern130 and has a predetermined height b.

Here, the predetermined height b refers to a height of the secondcircuit pattern 140 of the circuit pattern 150 except a filled portionof the corner portion of the first circuit pattern 130. In other words,the predetermined height b refers to a height of the second circuitpattern 140 protruding from the pure upper surface of the first circuitpattern 130 except the corner portion.

At this point, the height b of the second circuit pattern 140 may be ina range from 1 μm to 13 μm. Preferably, the height b of the secondcircuit pattern 140 may be in a range from 3 μm to 10 μm. Morepreferably, the height b of the second circuit pattern 140 may be in arange from 3 μm to 6 μm.

That is, when the height of the second circuit pattern 140 is more than1 μm, an overspreading phenomenon of the top metal layer according tothe embodiment of the present invention can be prevented. Further, whenthe height of the second circuit pattern 140 is in a range from 3 μm to6 μm, the protrusion of the top metal layer 160 is minimized, and theoverspreading phenomenon of the top metal layer 160 can be preventedcompletely.

Meanwhile, the lower surface of the top metal layer 160 includes acontact region in contact with the upper surface of the circuit pattern150 and a non-contact region which protrudes from the contact region tothe outside of the upper surface of the circuit pattern 150 and not incontact with the upper surface of the circuit pattern 150.

Here, a width of the non-contact region of the top metal layer 160 maybe in a range from 3 μm to 7 μm. Preferably, the width of thenon-contact region of the top metal layer 160 may be in a range from 3μm to 4 μm.

That is, with the second circuit pattern 140 of the circuit pattern 150not formed, when the top metal layer 160 is formed, the width of thenon-contact region of the top metal layer 160 is increased compared tothat of the embodiment of the present invention, and thus the width isgenerally in a range from 8 μm to 9 μm.

However, in the embodiment of the present invention, since the top metallayer 160 is formed after the second circuit pattern 140 of the circuitpattern 150 is formed, the width of the non-contact region of the topmetal layer 160 is minimized, and thus the non-contact region has awidth of 7 μm or less.

According to the embodiment of the present invention, a flash platingprocess is performed to fill corner portions of a circuit pattern etchedduring a preprocessing process, then a surface processing process isperformed with the corner portions filled, and thus a failure of the topmetal layer due to overspreading can be removed, thereby the reliabilityof a PCB can be improved.

In addition, according to the embodiment of the present invention, sincea top metal layer is formed by utilizing a plating seed layer used inthe formation of a circuit pattern, one of electrolytic surfaceprocessing and electroless surface processing methods is selectablewithout a design restriction.

Further, according to the embodiment of the present invention, since atop metal layer including gold (Au) is formed using the plating seedlayer used in the formation of the circuit pattern, a nickel (Ni) topmetal layer serving as a seed layer function of a conventional gold (Au)top metal layer can be removed, thus a thickness of a product can belowered, and product cost can also be lowered due to the removal of thenickel top metal layer.

Furthermore, according to the embodiment of the present invention, sincea portion, protruding from a side surface of the circuit pattern to theoutside, of the top metal layer is minimized by performing the flashplating process, the structural stability of the top metal layer can besecured.

Hereinafter, a method of manufacturing the PCB according to theembodiment of the present invention shown in FIG. 3 will be described indetail with reference to FIGS. 5 to 15.

FIG. 5 is a flowchart of a process sequence for describing the method ofmanufacturing the PCB according to the embodiment of the presentinvention, and FIGS. 6 to 15 are cross-sectional views of the processsequence for describing the method of manufacturing the PCB shown inFIG. 3.

Referring to FIG. 5, the PCB according to the embodiment of the presentinvention may be manufactured by the following manufacturing process.

First, the manufacture the PCB according to the embodiment of thepresent invention starts with a process of forming a pattern using apattern formation process (S110).

When the pattern is formed, a process of polishing a surface of thepattern is performed using a polishing process (S120).

Then, when the polishing process is performed, a part of the surface ofthe pattern is etched during a preprocessing process (S130).

Further, when the preprocessing process is completed, a process ofstacking dry films is performed to perform flash plating and surfaceprocessing plating (S140). Here, preferably, the dry films are stackedfor the surface processing plating. In other words, the flash platingmay be performed after the dry films are stacked, or alternatively, theflash plating may be performed in advance before the dry films arestacked.

Then, when the dry films are stacked, a plasma processing process isperformed on the surface of the formed pattern (S150).

At this point, the plasma processing process is performed selectivelyand is not a necessary process to be included. However, when the plasmaprocessing process was performed, a width or shape of a non-contactregion of the top metal layer 160 that was made was different and betterthan a width or shape made by performing the plasma processing process.Thus, in order to obtain a better result, it is preferable that theplasma processing process be performed.

When the plasma processing process is performed, a flash plating processis performed to fill corner portions of the pattern etched during thepreprocessing process (S160).

Then, when the flash plating process is completed, a top metalayer isformed on a layer formed by performing the flash plating (S170).

When the top metal layer is formed, a process of removing a seed layerused for forming the top metal layer and the pattern is performed(S180).

Hereinafter, each of the above processes will be described in detailwith reference to FIGS. 6 to 15.

First, referring to FIG. 6, an insulating layer 110 is provided, and aplating seed layer 120 is formed on the provided insulating layer 110.

The plating seed layer 120 may be formed on the insulating layer 110 byelectroless-plating of pure copper or a metal including copper.

The insulating layer 110 may be a thermosetting or thermoplastic polymerboard, a ceramic board, an organic-inorganic composition material board,or a fiberglass immersion board, and when a polymer resin is included,an epoxy-based insulating resin may be included, otherwise, apolyimide-based resin may be included.

That is, the insulating layer 110 is a plate on which an electricalcircuit capable of changing wirings is disposed and may include all ofprinting, a wiring plate, and an insulating board which are formed of aninsulating material which is able to form a conductive pattern on asurface of the insulating board.

The insulating layer 110 may be rigid or flexible. For example, theinsulating layer 110 may include glass or plastic. Specifically, theinsulating layer 110 may include a chemically tempered/semi-temperedglass, such as soda lime glass, aluminosilicate glass, etc., a temperedor flexible plastic such as polyimide (PI), polyethylene terephthalate(PET), propylene glycol (PPG), polycarbonate (PC), etc., or sapphire.

Further, the insulating layer 110 may include an optically isotropicfilm. For example, the insulating layer 110 may include cyclic olefincopolymer (COC), cyclic olefin polymer (COP), optically isotropic PC,optically isotropic polymethylmethacryate (PMMA), etc.

Further, the insulating layer 110 may have a curved surface which ispartially bent. That is, the insulating layer 110 may partially have aplane and may partially be bent having the curved surface. Specifically,an end portion of the insulating layer 110 may be bent having the curvedsurface, bent having a surface with a random curvature, or crooked.

Further, the insulating layer 110 may be a flexible board havingflexibility.

Further, the insulating layer 110 may be a curved or bent board. Here,the insulating layer 110 may form a wiring layout for electrical wiringswhich connect circuit components based on a circuit design, andelectrical conductors may be disposed thereon. Further, electricalcomponents may be mounted on the insulating layer 110, and theinsulating layer 110 may form wirings configured to connect theelectrical components to make a circuit, and may mechanically fix thecomponents besides functioning as electrically connecting thecomponents.

The plating seed layer 120 may use a general copper clad laminate (CCL)rather than being formed by electroless-plating on the surface of theinsulating layer 110.

At this point, when the plating seed layer 120 is formed byelectroless-plating, roughness may be introduced to the upper surface ofthe insulating layer 110 for performing easy plating.

An electroless-plating method may be processed by sequentiallyperforming a degreasing process, a soft corrosion process, a preliminarycatalyst processing process, a catalyst processing process, anactivation process, an electroless-plating process, and an oxidationprevention processing process. Further, the plating seed layer 120 maybe formed by sputtering metal particles using plasma instead of plating.

At this point, a de-smear process which removes smears of the surface ofthe insulating layer 110 may be additionally performed before platingthe plating seed layer 120. The de-smear process is performed to make asurface of the insulating layer 110 rough to make plating easy forforming the plating seed layer 120.

Next, referring to FIG. 7, a first mask 125 is formed on the platingseed layer 120. Here, the first mask 125 may use a dry film.

Here, the first mask 125 may include an opening (not shown) whichexposes at least a part of an upper surface of the plating seed layer120.

Here, the upper surface exposed by the opening of the first mask 125,which is a part of the upper surface of the plating seed layer 120,corresponds to a region in which a circuit pattern 150 may be formedlater.

In other words, the first mask 125 having the opening which exposes aportion of the upper surface of the plating seed layer 120 for formingthe circuit pattern 150 is formed on the plating seed layer 120.

At this point, the first mask 125 may be formed to cover the entireupper surface of the plating seed layer 120, and thus the opening may beformed by removing a part of a portion, in which the circuit pattern 150may be formed, of the formed first mask 125.

Next, the circuit pattern 150 under which the opening of the first mask125 is buried is formed on the plating seed layer 120. Preferably, afirst circuit pattern 130 of the circuit pattern 150 under which atleast a part of the opening of the first mask 125 is buried is formed onthe plating seed layer 120.

The first circuit pattern 130 of the circuit pattern 150 may be formedby electroplating a conductive material, e.g., preferably, an alloyincluding copper, on the plating seed layer 120 as a seed layer to buryat least a part of the opening of the first mask 125.

Then, referring to FIG. 8, when the first circuit pattern 130 of thecircuit pattern 150 is formed, a grinding process for planarization ofan upper surface of the first circuit pattern 130 of the formed circuitpattern 150 is performed.

While performing the grinding process, at least a part of the upperportion of the first circuit pattern 130 of the circuit pattern 150spreads into the first mask 125, and thus an upper end portion of thefirst circuit pattern 130 includes a protrusion (not shown) protrudingin a direction of the first mask 125.

Then, referring to FIG. 9, a preprocessing process for performing asurface processing process is performed.

Here, the preprocessing process is performed using an acid-basedchemical for etching a surface of first circuit pattern 130 of thecircuit pattern 150. At this point, when the preprocessing process isperformed, the etching is performed not only on the upper surface of thefirst circuit pattern 130 but also boundary surfaces of upper and sidesurfaces of the first circuit pattern 130.

Thus, when the preprocessing process is performed, a corner portion 135of the first circuit pattern 130 has a predetermined curvature in aconvex shape.

Here, the preprocessing process etches the surface of the first circuitpattern 130, and at this point, the etching is preferably performed in arange from 0.4 μm to 10 μm.

In other words, when the preprocessing process is performed, a gap isgenerated between the first mask 125 and first circuit pattern 130 ofthe circuit pattern.

Then, referring to FIG. 10, a flash plating process is performed to forma second circuit pattern 140 of the circuit pattern 150 on the firstcircuit pattern 130.

Here, the circuit pattern 150 includes the first circuit pattern 130 inwhich a corner portion of an upper portion has a predeterminedcurvature, and the second circuit pattern 140 which is formed on thefirst circuit pattern 130 and covers the corner portion of the firstcircuit pattern 130.

That is, the circuit pattern 150 includes the first circuit pattern 130in which boundary portions of the upper and side surfaces have convexlycurved surfaces by having the corner portions removed during thepreprocessing process.

Further, the second circuit pattern 140 is disposed on the first circuitpattern 130.

The second circuit pattern 140 is formed to cover the convexly curvedsurface of the first circuit pattern 130. In other words, the secondcircuit pattern 140 fills the corner portions of the first circuitpattern 130 removed during the preprocessing process.

An upper surface of the second circuit pattern 140 may be planar, and alower surface thereof may have a curvature corresponding to a curvatureof the corner portion of the first circuit pattern 130.

At least a part of a lower end of the second circuit pattern 140 ispositioned at a lower level than an upper end of the first circuitpattern 130.

That is, the second circuit pattern 140 is formed to cover the cornerportions of the first circuit pattern 130, and the corner portions areboundary surfaces of the upper and side surfaces of the first circuitpattern 130. In other words, the corner portions of the first circuitpattern 130 include a part of upper surface and a part of side surfacesof the first circuit pattern 130.

Accordingly, the second circuit pattern 140 is formed to substantiallycover a part of the upper and side surfaces of the first circuit pattern130.

Thus, a part of the lower end of the second circuit pattern 140 extendsup to a side surface portion of the first circuit pattern 130 and isthus positioned at a lower level than the upper end of the first circuitpattern 130.

Here, although it has been described that the circuit pattern 150 isprovided with the first circuit pattern 130 and the second circuitpattern 140 as a plurality of layers, since the first circuit pattern130 and the second circuit pattern 140 are formed of the same material,the first circuit pattern 130 and the second circuit pattern 140 aresubstantially formed as a single layer.

A lower surface of the first circuit pattern 130 of the circuit pattern150 is formed being in direct contact with the upper surface of theplating seed layer 120.

At this point, corner portions of an upper portion of the first circuitpattern 130 of the circuit pattern 150 are formed to have apredetermined curvature in a lengthwise direction. Preferably, thecorner portions of the first circuit pattern 130 are formed to have aconvex curvature in the lengthwise direction.

The corner portions are boundary portions of upper and side surfaces ofthe first circuit pattern 130 and thus include a part of the uppersurface and a part of the side surface.

Further, the second circuit pattern 140 of the circuit pattern 150 isformed on the first circuit pattern 130 and covers the corner portionsof the first circuit pattern 130.

That is, the lower surface of the second circuit pattern 140 of thecircuit pattern 150 is formed to have a predetermined curvaturecorresponding to a curvature of the corner portion of the first circuitpattern 130.

Meanwhile, the circuit pattern 150 includes the first circuit pattern130 and the second circuit pattern 140, wherein the second circuitpattern 140 is formed on the upper surface of the first circuit pattern130 and has a predetermined height b.

Here, the predetermined height b refers to a height of the secondcircuit pattern 140 of the circuit pattern 150 except a filled portionof the corner portion of the first circuit pattern 130. In other words,the predetermined height b refers to a height of the second circuitpattern 140 protruding from the pure upper surface of the first circuitpattern 130 except the corner portion.

At this point, the height b of the second circuit pattern 140 may be ina range from 1 μm to 13 μm. Preferably, the height b of the secondcircuit pattern 140 may be in a range from 3 μm to 10 μm. Morepreferably, the height b of the second circuit pattern 140 may be in arange from 3 μm to 6 μm.

That is, when the height of the second circuit pattern 140 is more than1 μm, an overspreading phenomenon of the top metal layer according tothe embodiment of the present invention can be prevented. Further, whenthe height of the second circuit pattern 140 is in a range from 3 μm to6 μm, the protrusion of the top metal layer 160 is minimized and theoverspreading phenomenon of the top metal layer 160 can be preventedcompletely.

Then, referring to FIG. 11, a second mask 155 having an opening whichexposes an upper surface of the circuit pattern 150, i.e., specifically,the upper surface of the second circuit pattern 140, is formed on thefirst mask 125.

The second mask 155 may include a dry film similar to the first mask125.

Then, referring to FIG. 12, by using the plating seed layer 120 and thecircuit pattern 150 as seed layers, the top metal layer 160 is formed onthe circuit pattern 150.

The top metal layer 160 is formed to have the same width as a width ofthe opening of the second mask 155.

The top metal layer 160 may be formed of a metal including only gold(Au) or may be formed of an alloy including gold (Au).

When the top metal layer 160 is formed of the alloy including gold (Au),the top metal layer 160 may be formed of a gold alloy including cobalt.At this point, the top metal layer 160 is formed by electroplating.

Preferably, the top metal layer 160 is formed by electroplating on theplating seed layer 120 which is the same layer as the plating seed layerused in the formation of the circuit pattern 150. That is, theelectroplating for the top metal layer 160 is performed due to anelectrical connection resulting from the connection between the platingseed layer 120 and the circuit pattern 150.

The top metal layer 160 is formed on the circuit pattern 150, and thus alower surface of the top metal layer 160 is in direct contact with theupper surface of the circuit pattern 150.

Then, referring to FIG. 13, when the top metal layer 160 is formed, thesecond mask 155 used for forming the top metal layer 160 is removed.

Then, referring to FIG. 14, when the second mask 155 is removed, thefirst mask 125 used for forming the circuit pattern 150 is removed.

When the first mask 125 is removed, as shown in FIG. 15, a process ofremoving the plating seed layer 120 formed on the insulating layer 110is performed. At this point, while performing the process of removingthe plating seed layer 120, a portion, formed under the circuit pattern150, of the plating seed layer 120 is not removed due to the circuitpattern 150, instead only a portion on which the circuit pattern 150 isnot formed is removed selectively.

At this point, an edge portion of the circuit pattern 150 is alsoremoved during the process of removing the plating seed layer 120.

That is, at least a part of side portions of the circuit pattern 150 isremoved together with the plating seed layer 120 while removing theplating seed layer 120.

Accordingly, the circuit pattern 150 may have a smaller width than thetop metal layer 160, and the top metal layer 160 protrudes from a sidesurface of the circuit pattern 150 to the outside.

The top metal layer 160 is formed on the circuit pattern 150, and thusthe lower surface of the top metal layer 160 is in direct contact withthe upper surface of the circuit pattern 150. More specifically, thelower surface of the top metal layer 160 is in direct contact with theupper surface of the second circuit pattern 140 of the circuit pattern150.

Here, the top metal layer 160 includes a lower surface having a widthgreater than a width of the upper surface of the circuit pattern 150.

Accordingly, the lower surface of the top metal layer 160 includes afirst lower surface in direct contact with the upper surface of thecircuit pattern 150 and a second lower surface not in contact with theupper surface of the circuit pattern 150.

Here, the first lower surface of the top metal layer 160 may be acentral region of the lower surface of the top metal layer 160, and thesecond lower surface of the top metal layer 160 may be left and rightregions of the top metal layer 160.

Further, the top metal layer 160 may have a shape in which widths ofupper and lower surfaces are the same.

Meanwhile, the upper and lower surfaces of the top metal layer 160 mayhave widths greater than that of the lower surface of the circuitpattern 150.

Meanwhile, the lower surface of the top metal layer 160 includes acontact region in contact with the upper surface of the circuit pattern150 and a non-contact region not in contact with the upper surface ofthe circuit pattern 150 by protruding from the contact region to theoutside of the upper surface of the circuit pattern 150.

Here, a width of the non-contact region of the top metal layer 160 maybe in a range from 3 μm to 7 μm. Preferably, the width of thenon-contact region of the top metal layer 160 may be in a range from 3μm to 4 μm.

That is, with the second circuit pattern 140 of the circuit pattern 150not formed, when the top metal layer 160 is formed, the width of thenon-contact region of the top metal layer 160 is increased compared tothat of the embodiment of the present invention, and thus the width isgenerally in a range from 8 μm to 9 μm.

However, in the embodiment of the present invention, since the top metallayer 160 is formed after the second circuit pattern 140 of the circuitpattern 150 is formed, the width of the non-contact region of the topmetal layer 160 is minimized, and thus the non-contact region has awidth of 7 μm or less.

As described above, according to the embodiment of the presentinvention, a flash plating process is performed to fill corner portionsof a circuit pattern etched during a preprocessing process, then asurface processing process is performed with the corner portions filled,and thus a failure of the top metal layer due to overspreading can beremoved, thereby the reliability of a PCB can be improved.

Further, according to the embodiment of the present invention, since atop metal layer is formed by utilizing a plating seed layer used in theformation of a circuit pattern, one of electrolytic surface processingand electroless surface processing methods is selectable without adesign restriction.

Further, according to the embodiment of the present invention, since atop metal layer including gold (Au) is formed using the plating seedlayer used in the formation of the circuit pattern, a nickel (Ni) topmetal layer serving as a seed layer function of a conventional gold (Au)top metal layer can be removed, and thus a thickness of a product can belowered, and product cost can also be lowered due to the removal of thenickel top metal layer.

Further, according to the embodiment of the present invention, since aportion, protruding from a side surface of the circuit pattern to theoutside, of the top metal layer is minimized by performing the flashplating process, the structurally stability of the top metal layer canbe secured.

As described above, the object, constitution, and effects described inthe embodiments are included at least one embodiment but are notnecessarily limited to one embodiment. Furthermore, the object,constitution, and effects described in each embodiment can be easilymodified into other concrete forms by one skilled in the art withoutchanging the technical spirit or the essential features of the presentinvention. Therefore, it should be understood that all modified orchanged forms derived from claims and their equivalents fall within thescope of the present invention.

Although the embodiments have been described based on a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised that fall within thespirit and scope of the principles of this disclosure by those skilledin the art. More particularly, numerous variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, thedrawings, and the appended claims.

What is claimed is:
 1. A printed circuit board comprising: an insulatinglayer; a plating seed layer disposed on the insulating layer; a circuitpattern disposed on the plating seed layer; and a top metal layerdisposed on the circuit pattern, wherein the circuit pattern comprises:a first circuit pattern disposed on the plating seed layer, and a secondcircuit pattern disposed on the first circuit pattern and including asame metallic material as the first circuit pattern.
 2. The printedboard of claim 1, wherein the top metal layer is formed of gold (Au). 3.The printed board of claim 2, wherein a lower surface of the top metallayer has a wider width than a width of an upper surface of the secondcircuit pattern.
 4. The printed board of claim 3, wherein the lowersurface of the top metal layer comprises: a first portion contacted withthe upper surface of the second circuit pattern, and a second portionspaced apart from the plating seed layer, the first and second circuitpatterns by a predetermined distance.
 5. The printed board of claim 4,wherein a length of the second portion of the top metal layer issatisfactorily in a range from 3 μm to 7 μm.
 6. The printed board ofclaim 3, wherein the lower surface of the top metal layer has a widerwidth than a width of the plating seed layer.
 7. The printed board ofclaim 3, wherein the lower surface of the top metal layer has a widerwidth than a width of the first circuit pattern.
 8. The printed board ofclaim 2, wherein the plating seed layer is formed of copper (Cu).
 9. Theprinted board of claim 8, wherein the first and second circuit patternsare formed of copper (Cu).
 10. The printed board of claim 9, wherein athickness of the second circuit pattern is thinner than a thickness ofthe first circuit pattern.
 11. The printed board of claim 9, wherein athickness of the second circuit pattern is satisfactorily in a rangefrom 1 μm to 13 μm.
 12. The printed board of claim 9, wherein athickness of the second circuit pattern is satisfactorily in a rangefrom 3 μm to 10 μm.
 13. The printed board of claim 9, wherein athickness of the second circuit pattern is satisfactorily in a rangefrom 3 μm to 6 μm.
 14. The printed board of claim 9, wherein a lowersurface of the second circuit pattern has a longer length than a lowersurface of the plating seed layer.
 15. The printed board of claim 9,wherein a part of a lower surface of the second circuit pattern ispositioned at a lower level than an upper surface of the first circuitpattern.
 16. A printed circuit board comprising: an insulating layer; aplating seed layer disposed on the insulating layer; a first circuitpattern disposed on the plating seed layer and directly contacted withthe plating seed layer; a second circuit pattern directly contacted withthe first circuit pattern and formed of copper; and a top metal layerdirectly contacted with the second circuit pattern and formed of gold(Au), wherein the top metal layer has a wider width than a width of thesecond circuit pattern.
 17. The printed board of claim 16, wherein alower surface of the top metal layer comprises: a first portion directlycontacted with the upper surface of the second circuit pattern, and asecond portion spaced apart from the plating seed layer, the first andsecond circuit patterns by a predetermined distance.
 18. The printedboard of claim 17, wherein a length of the second portion of the topmetal layer is satisfactorily in a range from 3 μm to 7 μm.
 19. Theprinted board of claim 16, wherein the plating seed layer and the firstcircuit pattern are formed of copper (Cu).
 20. The printed board ofclaim 19, wherein a thickness of the second circuit pattern is thinnerthan a thickness of the first circuit pattern.